A spark plug for an internal combustion engine generally is comprised of a rod-like central electrode, a hollow cylindrical ceramic insulator encasing the central electrode, a conductive terminal attached to the central electrode at the spark plug terminal end, a hollow cylindrical metal shell partially encasing the ceramic insulator having threads for mating the spark plug with the engine block, a hexagonal nut for gripping the plug with a wrench, and an L-shaped ground electrode attached to the ignition end of the metal shell.
When the spark plug is installed in the engine compartment, the threads are mated to the engine block with the ignition end accessing the combustion chamber. The ignition coil is connected to the terminal end of the spark plug via ignition wires going from the ignition coil to the spark plug terminal end. The ignition coil wire is attached to the spark plug terminal with a clip.
In some cases, space around the spark plug is severely limited. Therefore, installation, removal and servicing of the spark plug can be difficult. There are several ways of handling this problem. Sometimes, other components in the engine compartment need to be removed to give access to the spark plug. Another solution uses a modified clip design that limits the space required for the plug stem plus clip. Still other methods use special spark plug wrenches that permit working in a limited space. Another approach is to use special spark plug designs that shorten the length of the spark plug between the spark plug hexagonal nut and the terminal end. All these solutions have utility in some situations. However none of these solutions are totally satisfactory.